“Topping-mediated” VOCs emitted by cotton plants
Electroantennogram response of two
major noctuid pests
Introduction
Material and methods
Results
Conclusion
Odor collection and analysis
Odors were collected by SPME from topped and non-topped plants in a greenhouse, and analyzed by GC-MS techniques.
Electroantennogram
Response of Helicoverpa armigera and
Spodoptera littoralis gravid females (3-7
days old) to cotton VOCs was tested using EAG techniques.
Behavioral tests should be conducted to evaluate possible deterrence of topping-mediated VOCs for egg-laying females and attraction for parasitoids. Induction of non-topped plants suggests high potential for integrated pest management.
“Topping-mediated” VOCs
We identified five “topping-mediated” VOCs, emitted in larger amounts by topped plants 4-16 days after topping for α-pinene, β-pinene,
myrcene and p-cymene, and 8-32 days after topping for
(E)-caryophyllene (Fig. 1).
The concurrent increase of these VOCs from non-topped neighboring plants also suggests partial induction.
The purpose of this study was to test the hypothesis that manual topping could affect the profile of plant volatile compounds (VOCs) emitted cotton by plants, which may in return affect moth behavior.
M. Marchand1, L. Dormont2, B. Schatz2,
I. Téréta3, A. Renou1 & T. Brévault1
1CIRAD, UPR 102, F-34398 Montpellier, France 2CEFE, UMR 5175 CNRS, F-34293 Montpellier, France
3IER, CRRA, BP 16, Sikasso, Mali
Damaged boll. Cotton square devoured by H. armigera.
Figure 1. VOCs collected from ( ) topped plants, ( ) non-topped neighboring
plants and ( ) non-topped controls.
Field experiments conducted in Mali showed a reduction of bollworm infestation on
cotton plants topped after the onset of flowering, as well as on non-topped neighboring
plants.
Lab bioassays for assessing larval mortality (Ph.Brévault)
Electroantennography on gravid Helicoverpa armigera and
Spodoptera littoralis females (Lepidoptera: Noctuidae) showed
that moths can detect topping-mediated VOCs (Fig. 2).
EAG response
Figure 3. EAG response of S. littoralis (top) and H. armigera (down) to VOCs emitted by cotton (in orange: topping-mediated compounds).
© Marchand control 0.1 % 1 % 10 % 100 % control * * * 0 20 40 β-pinene * * * 0 20 40 α-pinene * * * 0 20 40 myrcene * * 0 50 100 150 200 250 300 0 20 40 Surfac e
Days post topping
p-cymene * * * 0 20 40 (E)-caryophyllene a ab abc abc abc bc bc cd d d 0.00 1.00 2.00 3.00 4.00 5.00 6.00
cis 3 hexenol α-pinène myrcène β-pinène limonène ocimène trans caryophyllène
α-humulène temoin vide temoin hexane ré ponse ( m V ) a ab ab ab ab b b b c c 0.00 1.00 2.00 3.00 4.00 5.00 6.00
cis-3-hexenol α-pinène p-cymène myrcène ocimène β-pinène trans caryophyllène
α-humulène témoin vide témoin hexane ré ponse ( m V ) H. armigera. S. littoralis SPME
